Electron traps and scintillation mechanism in YAlO3 : Ce and LuAlO3 : Ce scintillators

In this paper we present the results of thermoluminescence, isothermal deca y and scintillation light yield measurements on two isostructural scintilla tor materials, YAlO3 : Ce and LuAlO3 : Ce. Ln addition to the variety of de ep traps identified by thermoluminescence and isothermal decays, scintillat ion light yield experiments demonstrate the presence in both materials of a number of relatively shallow traps. While the deep traps may reduce the sc intillation light yield, they do not influence the kinetics of the process. The shallow traps, on the other hand, by interfering with the process of r adiative recombination of charge carriers via Ce3+ ions, can strongly affec t not only the yield of the scintillation process but its kinetics as well. The presence of shallow traps provides a consistent explanation for a numb er of poorly understood relationships between the two scintillator material s, including a higher room temperature scintillation light yield and longer scintillation decay time in YAlO3 :Ce, and a longer scintillation rise tim e in LuAlO3:Ce. Theoretical analysis indicates that elimination of these tr aps would make the two materials nearly identical in scintillator performan ce. Although the specific identity of all traps remains elusive, the perfor mance of both scintillator materials is now, in practical terms, fully unde rstood. (C) 1998 Elsevier Science B.V. All rights reserved.